diff --git a/cmdline/handle.c b/cmdline/handle.c
index 1172e67a..d721f045 100644
--- a/cmdline/handle.c
+++ b/cmdline/handle.c
@@ -567,7 +567,7 @@ struct snapraid_handle* handle_mapping(struct snapraid_state* state, unsigned* h
 		map = 0;
 		for (k = state->maplist; k != 0; k = k->next) {
 			map = k->data;
-			if (strcmp(disk->name, map->name) == 0)
+			if (pathcmp(disk->name, map->name) == 0)
 				break;
 		}
 		if (!map) {
diff --git a/cmdline/selftest.c b/cmdline/selftest.c
index bbb0764e..8c0a59d4 100644
--- a/cmdline/selftest.c
+++ b/cmdline/selftest.c
@@ -1930,6 +1930,24 @@ static void test_disk_name(void)
 	assert(disk_name_invalid_reason("r-parity") != 0);
 	assert(disk_name_invalid_reason("z-parity") != 0);
 
+#ifdef _WIN32
+	/* case-insensitive parity names rejected on Windows */
+	assert(disk_name_invalid_reason("PARITY") != 0);
+	assert(disk_name_invalid_reason("Parity") != 0);
+	assert(disk_name_invalid_reason("1-PARITY") != 0);
+	assert(disk_name_invalid_reason("2-PARITY") != 0);
+	assert(disk_name_invalid_reason("Q-PARITY") != 0);
+	assert(disk_name_invalid_reason("Z-PARITY") != 0);
+#else
+	/* case-sensitive on Unix: uppercase variants are distinct from reserved lowercase parity names */
+	assert(disk_name_invalid_reason("PARITY") == 0);
+	assert(disk_name_invalid_reason("Parity") == 0);
+	assert(disk_name_invalid_reason("1-PARITY") == 0);
+	assert(disk_name_invalid_reason("2-PARITY") == 0);
+	assert(disk_name_invalid_reason("Q-PARITY") == 0);
+	assert(disk_name_invalid_reason("Z-PARITY") == 0);
+#endif
+
 	/* valid names containing parity as substring */
 	assert(disk_name_invalid_reason("parity1") == 0);
 	assert(disk_name_invalid_reason("parity_data") == 0);
diff --git a/cmdline/snapraid.c b/cmdline/snapraid.c
index 0625692e..1c21f401 100644
--- a/cmdline/snapraid.c
+++ b/cmdline/snapraid.c
@@ -178,16 +178,18 @@ void log_open(const char* file)
 
 void log_close(const char* file)
 {
-	if (stdlog != stdout && stdlog != stderr && stdlog != 0) {
-		if (fclose(stdlog) != 0) {
+	FILE* log = stdlog;
+
+	/* fclose() invalidates the stream even on error, so fatal reporting must use stderr. */
+	stdlog = 0;
+	if (log != stdout && log != stderr && log != 0) {
+		if (fclose(log) != 0) {
 			/* LCOV_EXCL_START */
 			log_fatal(errno, "Error closing the log file '%s'. %s.\n", file, strerror(errno));
 			exit(EXIT_FAILURE);
 			/* LCOV_EXCL_STOP */
 		}
 	}
-
-	stdlog = 0;
 }
 
 /****************************************************************************/
diff --git a/cmdline/state.c b/cmdline/state.c
index 568a235f..0dadf667 100644
--- a/cmdline/state.c
+++ b/cmdline/state.c
@@ -117,6 +117,9 @@ static int lev_config_scan(const char* s, unsigned* level, unsigned* mode)
 const char* disk_name_invalid_reason(const char* name)
 {
 	unsigned dummy_level;
+#ifdef _WIN32
+	char lower[DISK_NAME_MAX + 1];
+#endif
 
 	if (strlen(name) > DISK_NAME_MAX)
 		return "Name is too long (maximum 127 bytes)";
@@ -126,8 +129,16 @@ const char* disk_name_invalid_reason(const char* name)
 		return "Name contains '\\'";
 	if (strchr(name, ':') != 0)
 		return "Name contains ':'";
+
+#ifdef _WIN32
+	pathcpy(lower, sizeof(lower), name);
+	strlwr(lower);
+	if (lev_config_scan(lower, &dummy_level, 0) == 0)
+		return "Name is a reserved parity name";
+#else
 	if (lev_config_scan(name, &dummy_level, 0) == 0)
 		return "Name is a reserved parity name";
+#endif
 
 	return 0;
 }
@@ -1081,7 +1092,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 			/* check if the disk name already exists */
 			for (i = state->disklist; i != 0; i = i->next) {
 				disk = i->data;
-				if (strcmp(disk->name, buffer) == 0)
+				if (pathcmp(disk->name, buffer) == 0)
 					break;
 			}
 			if (i) {
@@ -1093,7 +1104,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 
 			for (i = state->extralist; i != 0; i = i->next) {
 				struct snapraid_extra* found_extra = i->data;
-				if (strcmp(found_extra->name, buffer) == 0)
+				if (pathcmp(found_extra->name, buffer) == 0)
 					break;
 			}
 			if (i) {
@@ -1203,7 +1214,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 			/* check if the disk name already exists */
 			for (i = state->extralist; i != 0; i = i->next) {
 				extra = i->data;
-				if (strcmp(extra->name, buffer) == 0)
+				if (pathcmp(extra->name, buffer) == 0)
 					break;
 			}
 			if (i) {
@@ -1215,7 +1226,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 
 			for (i = state->disklist; i != 0; i = i->next) {
 				struct snapraid_disk* found_disk = i->data;
-				if (strcmp(found_disk->name, buffer) == 0)
+				if (pathcmp(found_disk->name, buffer) == 0)
 					break;
 			}
 			if (i) {
@@ -1316,7 +1327,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 				struct snapraid_disk* found_disk = 0;
 				for (i = state->disklist; i != 0; i = i->next) {
 					struct snapraid_disk* disk = i->data;
-					if (strcmp(disk->name, buffer) == 0) {
+					if (pathcmp(disk->name, buffer) == 0) {
 						found_disk = disk;
 						break;
 					}
@@ -1324,7 +1335,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 				struct snapraid_extra* found_extra = 0;
 				for (i = state->extralist; i != 0; i = i->next) {
 					struct snapraid_extra* extra = i->data;
-					if (strcmp(extra->name, buffer) == 0) {
+					if (pathcmp(extra->name, buffer) == 0) {
 						found_extra = extra;
 						break;
 					}
@@ -1385,7 +1396,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 				struct snapraid_disk* found_disk = 0;
 				for (i = state->disklist; i != 0; i = i->next) {
 					struct snapraid_disk* disk = i->data;
-					if (strcmp(disk->name, buffer) == 0) {
+					if (pathcmp(disk->name, buffer) == 0) {
 						found_disk = disk;
 						break;
 					}
@@ -1393,7 +1404,7 @@ void state_config(struct snapraid_state* state, const char* path, const char* co
 				struct snapraid_extra* found_extra = 0;
 				for (i = state->extralist; i != 0; i = i->next) {
 					struct snapraid_extra* extra = i->data;
-					if (strcmp(extra->name, buffer) == 0) {
+					if (pathcmp(extra->name, buffer) == 0) {
 						found_extra = extra;
 						break;
 					}
@@ -1705,7 +1716,7 @@ static struct snapraid_disk* find_disk_by_name(struct snapraid_state* state, con
 
 	for (i = state->disklist; i != 0; i = i->next) {
 		struct snapraid_disk* disk = i->data;
-		if (strcmp(disk->name, name) == 0)
+		if (pathcmp(disk->name, name) == 0)
 			return disk;
 	}
 
@@ -1804,7 +1815,7 @@ static void state_map(struct snapraid_state* state)
 		/* check if the disk is already mapped */
 		for (j = state->maplist; j != 0; j = j->next) {
 			map = j->data;
-			if (strcmp(disk->name, map->name) == 0) {
+			if (pathcmp(disk->name, map->name) == 0) {
 				/* mapping found */
 				break;
 			}
@@ -2096,7 +2107,7 @@ static void state_content_check(struct snapraid_state* state, const char* path)
 		tommy_node* j;
 		for (j = i->next; j != 0; j = j->next) {
 			struct snapraid_map* other = j->data;
-			if (strcmp(map->name, other->name) == 0) {
+			if (pathcmp(map->name, other->name) == 0) {
 				/* LCOV_EXCL_START */
 				log_fatal(ECONTENT, "Conflicting 'map' disk specification in '%s'\n", path);
 				exit(EXIT_FAILURE);
diff --git a/cmdline/support.c b/cmdline/support.c
index 62188239..bc7fe19d 100644
--- a/cmdline/support.c
+++ b/cmdline/support.c
@@ -375,27 +375,31 @@ static void msg(FILE* out, const char* format, ...)
 
 void vlog_fatal(int err, const char* format, va_list ap, const char* post)
 {
+	int log_failed = 0;
+
 	lock_msg();
 
 	if (stdlog) {
 		if (is_hw(err))
-			fprintf(stdlog, "msg:fatal_hardware: ");
+			log_failed = fprintf(stdlog, "msg:fatal_hardware: ") < 0;
 		else
-			fprintf(stdlog, "msg:fatal: ");
+			log_failed = fprintf(stdlog, "msg:fatal: ") < 0;
 
 		va_list ap_copy;
 		va_copy(ap_copy, ap);
-		vfprintf(stdlog, format, ap_copy);
+		if (vfprintf(stdlog, format, ap_copy) < 0)
+			log_failed = 1;
 		va_end(ap_copy);
 
-		if (post)
-			fprintf(stdlog, "%s", post);
+		if (post && fprintf(stdlog, "%s", post) < 0)
+			log_failed = 1;
 
-		fflush(stdlog);
+		if (fflush(stdlog) != 0)
+			log_failed = 1;
 	}
 
-	/* GUI consumers read tagged fatal messages from the log and must not receive a duplicate raw copy. */
-	if (!stdlog || msg_fatal_stderr) {
+	/* A failed tagged write must retain stderr as the only usable fatal diagnostic. */
+	if (!stdlog || log_failed || msg_fatal_stderr) {
 		va_list ap_copy2;
 		va_copy(ap_copy2, ap);
 		vmsg(stderr, format, ap_copy2);
diff --git a/cmdline/support.h b/cmdline/support.h
index dbc551a2..98af27cd 100644
--- a/cmdline/support.h
+++ b/cmdline/support.h
@@ -93,7 +93,7 @@ typedef void log_ptr(int err, const char* format, ...) __attribute__((format(att
  * Messages printed before an early termination.
  *
  * These messages go in the log file and in stderr, except in GUI mode
- * when a log is configured, where only the tagged log message is emitted.
+ * when the tagged log message is emitted successfully.
  */
 void vlog_fatal(int err, const char* format, va_list ap, const char* post);
 void log_fatal(int err, const char* format, ...) __attribute__((format(attribute_printf, 2, 3)));